This invention relates to a control unit assembly for use with a medical device and, particularly, a pneumatic medical device, such as a compression device for a limb. In particular, the invention relates to a control unit assembly for use with a mobile compression device suited for use in the treatment of venous leg ulcers, oedema, deep vein thrombosis and vascular disorders.
Various medical devices are known that require inflation of one or more cells with fluid to a desired pressure, for example, compression devices which are used to apply pressure or pressure offloading devices such as mattresses or cushions which are used to even out pressure points. Compression devices are known for applying compressive pressure to a patient's limb. These types of devices are used to assist mainly in the prevention of deep vein thrombosis (DVT), vascular disorders and the reduction of oedema. Prior art devices are adapted for use in a hospital setting in which they are used predominantly for the prevention of DVT in patients with a high risk for developing this condition. U.S. Pat. Nos. 5,117,812; 5,022,387; 5,263,473; 6,231,532; 6,440,093 and 6,463,934 disclose such devices.
Compression therapy is used in the treatment of venous leg ulcers. The treatment relies on the compression achieving a reduction in oedema and improved return of blood via the venous system. This in turn reduces the residence time for blood supplied to the lower limb and the severity of ischaemic episodes within the limb that can result in tissue breakdown.
Compression of the limb can be achieved by a pneumatic or hydraulic compression device.
WO 2004/084790 discloses one type of mobile compression device. By “mobile” it is meant that the user wearing the compression device has relative freedom to move about. The device of WO 2004/084790 comprises one or more fluid inflatable cuffs containing one or more cells arranged for fitting on to a leg or an arm. The device allows the adjustment of the pressure in the cells dependent on the pressure profile desired. The application of pressure by the cells in the sleeve or cuff is maintained by a pump and valves which are operated by an automatic control unit which detects the fall or rise in pressure in each cell throughout the device. Where excessive or deficient pressure is detected by a sensor located in the cell, the control unit activates the pump to restore the intended pressure.
In the compression devices of the prior art, the control unit is a separate component which is typically not integral to the compression device and remotely operated. This is often on the user's belt, placed in a pocket or carried around by hand which is inconvenient for the user.
As a control unit, generally, includes a pump, electronic circuitry, conduits for connecting the control unit to the compression device, valves, a source of power, etc., the control unit is usually quite large. Hence, the known control units are bulky and heavy. Therefore, positioning of the unit in the device has not been practical because attaching the known control units to an outer surface of the compression device would result in an excessive weight burden impairing the mobility of the user. Integral positioning is also unnecessary as most of the prior art devices are used in a hospital setting where mobility of the patient is not the main concern. Were the control unit to be positioned on the device, weight would be localized at the attachment point of the device resulting in a weight imbalance on the compression device. Also, a bulky control unit protruding from an outer surface of the compression device permits the unit to be knocked and possibly broken when the user is mobile and would not fit beneath clothing.
There are barriers to reducing the size of the control unit. The conduits between the pump and the inflatable cells have in the past been external and would thus present a trip or tangle hazard. The power consumption by the components in a typical hospital device would make the battery too large to be carried on the device itself and would make it too bulky to fit under clothing.
The above disadvantages may contribute to low patient compliance and limit use. A control unit which is an integral part of a device with a low profile and whose internal components are miniaturized sufficiently so as not to affect the performance of the control unit or the medical device has therefore been sought.